How to Reset forgotten Root Password in Suse Enterprise Linux

by George Sruthin | Feb 4, 2024 | Hosting, Linux, Servers, VPS

To reset forgotten password hard reboot your affected VM or bare metal server, press arrow key to skip boot timeout from grub, then press “e”

search for line start with “linuxefi” (some time instead of “linuxefi” you can find “linux” or “linux16”) and press “end” button

at the end of the line type init=/bin/bash then press F10 or ctrl+x to boot

now you can will be booted into shell, but it will in readonly mode, to change to read, write mode type following commands

mount -o rw, remount /

after that type

chroot /

to reset password type following command followed by user name.

passwd root

then type exit and
type reboot

Enjoy



you can also find related topic.

How to reset forgotten the root password in ubuntu server

How to reset forgotten root password in freebsd

Source

Installing Kali-Linux 64-Bit on Raspberry Pi-4

by Teffin Varghese | Oct 31, 2021 | Hosting, Howtos, Linux, Networking, OS, Review, Security, Servers, Troubleshooting, Unix, VPN, VPS, Vulnerability, Workstation

Installing Kali-Linux (64-bit) in Raspberry Pi-4

For the 64-Bit OS support we need to use Raspberry Pi 4
I’m using Raspberry Pi 4 Model-B With * Gigs of RAM, A 4GB RAM model would work just fine.

But First what is Raspberry Pi and what is it used for ?

he Raspberry Pi is a low cost, credit-card sized computer that plugs into a computer monitor or TV, and uses a standard keyboard and mouse.
It is a capable little device that enables people of all ages to explore computing, and to learn how to program in languages like Scratch and Python.
It’s capable of doing everything you’d expect a desktop computer to do, from browsing the internet and playing high-definition video, to making spreadsheets, word-processing, and playing games.

What’s more, the Raspberry Pi has the ability to interact with the outside world, and has been used in a wide array of digital maker projects, from music machines and parent detectors to weather stations and tweeting birdhouses with infra-red cameras.
We want to see the Raspberry Pi being used by kids all over the world to learn to program and understand how computers work.

For further details, Checkout their cool website

Now please follow the following steps to install Kali-Linux on a Raspberry Pi 4

Step 1

Assemble and enclose the Raspberry Pi, We recommend a case with passive cooling or with a small fan and heat-sinks.
Yes of course you can the Pi without any case or cooling setup, But we recommend to use a cooling case for protection and better performance.

Step 2

Download Kali-Linux Image from the official website.
You can get the download link from the below URL.
You need to select ARM image category, then choose the Raspberry Pi 64-bit Image.

Click Here to download

Step 3

Now you need to write this image to a Micro SD card, Which you are going to use it on your Raspberry Pi.
You can use either Balena Etcher or the official Raspberry Pi imager for this task.

Here we are using the official Raspberry Pi imager. You can download the imager from the following URL.
https://www.raspberrypi.com/software/
Here is the download link for Windows machines
https://downloads.raspberrypi.org/imager/imager_1.6.2.exe

Imager Latest Version

Step 4

Write Kali-Linux image to the Micro SD-Card. Please follow the following images.

1, Launch the Pi Imager and select Choose OS.

2, Select the option “Use Custome” for our Kali-Linux Image

3, Browse and choose the Kali-Linux Image we have downloaded from our PC.

4, Now select storage and choose our micro SD-Card and click write to write the Image.

Note: Please make sure you have selected the correct storage, In our case the SD-Card. If you choose the wrong location the imager will wipe the selected storage location.

step 5
Insert the Micro SD-card to your Raspberry Pi. Plug in your Raspberry Pi Power-Brick to the device and
connect your Pi to a monitor, also plugin your Mouse and Keyboard as well, Then power-on the power brick.

It will take some time for the initial bootup, Wait for it. If everything is perfect your Raspberry Pi will boot into Kali-Linux.

That’s it, Have fun.

Disabling weak CBC ciphers in ssh Redhat

by George Sruthin | Jul 18, 2021 | Linux, Security, Servers, Vulnerability

Today we will cover how to disable weak cbc ciphers in ssh server, after this you will pass cbc ciphers vulnerability.

Environment

Red Hat Enterprise Linux 8.x
OpenSSH

Tool used for vulnerability checking

Tenable.sc

Resolution

There were 2 server affected in total so i will try to do explain in three parts, First part consist adding policy (optional), Second is enabling specific policy instead of default site-wide policy, Third part has 2 methods for me both has worked, you can choose one of them.

Step 1

First open terminal and type

update-crypto-policies --show

by default you will get reply as

DEFAULT

then please change it to FUTURE, for that type

update-crypto-policies --set FUTURE

reboot server, most probably this wont work, for me also it didn't work, i included this because in every tutorial it is mentioned. now go to step 2.

Step 2

to enable specific CRYPTO_POLICY instead of using system-wide policy, you need to uncomment the line " CRYPTO_POLICY" from /etc/sysconfig/sshd

Open /etc/sysconfig/sshd and uncomment from .

#CRYPTO_POLICY=

to:

CRYPTO_POLICY=

Step 3

Disable CBC Ciphers

Now we need to set SSHD specific policy for CBC ciphers, you can do this by modifying line found in /etc/ssh/sshd_config.

after adding method 1 to /etc/ssh/sshd_config , during restarting ssh server you may face issue, just commend before public key, and it worked for me, to find why ssh server failed to start you can use following command.

sshd -t

edit /etc/ssh/sshd_config and add following lines, in Method 1 you may face issue when trying to restart ssh server, type

Oh i forgot to mention that its always good to take back of config files before make any changes.

CBC Ciphers Method 1

[email protected],[email protected],aes256-ctr,[email protected],aes128-ctr GSSAPIKexAlgorithms=gss-gex-sha1-,gss-group14-sha1- [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1 HostKeyAlgorithms=rsa-sha2-256,[email protected],ecdsa-sha2-nistp384,[email protected],rsa-sha2-512,ecdsa-sha2-nistp521,[email protected],ssh-ed25519,[email protected],ssh-rsa,[email protected] PubkeyAcceptedKeyTypes=rsa-sha2-256,ecdsa-sha2-nistp256,[email protected],ecdsa-sha2-nistp384,[email protected],rsa-sha2-512,ecdsa-sha2-nistp521,[email protected],ssh-ed25519,[email protected],ssh-rsa,[email protected]

restart sshd to apply changes, for that type

systemctl restart sshd

CBC Ciphers Method 2

Protocol 2 HostKey /etc/ssh/ssh_host_ed25519_key HostKey /etc/ssh/ssh_host_rsa_key KexAlgorithms [email protected],diffie-hellman-group-exchange-sha256 Ciphers [email protected],[email protected],[email protected],aes256-ctr,aes192-ctr,aes128-ctr MACs [email protected],[email protected],[email protected],hmac-sha2-512,hmac-sha2-256,[email protected]

restart sshd to apply changes, for that type

systemctl restart sshd

disabling weak cbc ciphers in ssh redhat

Now you can do vulnerability test again, it must be fix by now, Enjoy

How to reset forgotten root password in FreeBSD.

by Teffin Varghese | Sep 29, 2020 | Hosting, Howtos, Linux, OS, Servers, Troubleshooting, VPS

Introduction.

FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.

FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution, which was based on Research Unix. The first version of FreeBSD was released in 1993.

Now lets check how can we reset forgotten root password in FreeBSD.

Step #1 : Reboot / Restart the server and boot into Single user mode.

You can press "S" at the boot prompt for entering the Single user mode.

Step #2: Mount the filesystem on the server.

root filesystem will be mounted read-only by default, you will need to remount it using the mount -ruw / command to give yourself read/write access. Run mount -a to remount all filesystems specified in the /etc/fstab file.

Step #3: Reset the root password.

You can reset the root password using the command passwd and set a new password on the server.

Step #4: Reboot the server.

That's it, when the server boots back to the OS you can login with the new password.

Cheers!!!

Please check our recent post about how to reset ubuntu server forgotten password.

How to Reset forgotten the Root Password in ubuntu server

by George Sruthin | Sep 24, 2020 | Hosting, Linux, Servers, VPS

Introduction

If you forget your root password of your ubuntu server you can use this method.

If you are using a bare metal server or a vps all you have to do is restart your server and press escape "ESC" key.

this will prevent Server OS to boot and bring up the GRUB boot promt. if you skip this step and boot in to OS then you need to restart your server again.

At the GRUB boot promt, press " E " to edit the first boot option which will be " Ubuntu "

Find kernal line starting with

 linux /boot/

add space in the end of that line and add this command

init=/bin/bash

Press CTRL + X or F10 to boot into single-user mode.

the system will boot and you will see the root prompt.

 mount -o remount,rw /

type above command to mount the system volume, for me it gives me an error but works.

now type command to reset your password.

passwd

This will ask you to type your password twice to confirm then reboot the server.

Hope this will help you, if you have any question please let me know.

MySQL Bin Files Eating Lots of Disk Space (fix)

by George Sruthin | Aug 23, 2020 | Hosting, Howtos, Linux, MySQL, Servers, VPS

Some time you may find MySQL stopped working and failed to start, and if you check status of MySQL using "systemctl status mysql" or "journalctl -xe" you can find that your "filesystem is out of space"

Trouble Shooting

OK first of all, we have to determine which disk partition is full, MySQL can be configured to store data on different disk or partition. by default it will be stored in /var/lib/mysql , i am going to use df command and find out how much space it uses, btw my vps has 20Gb of file system.


root@testserver:~# du -sh /var/lib/mysql
13G    /var/lib/mysql
root@coversunkochi:~#
root@coversunkochi:~# lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda       8:0    0 19.1G  0 disk
├─sda1    8:1    0   19G  0 part /
├─sda14   8:14   0    1M  0 part
└─sda15   8:15   0   61M  0 part /boot/efi
root@coversunkochi:~#
root@coversunkochi:~# df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        19G  18.6G   403M  99% /

As you can see my vps has a root directory of 19 Gb and /var/lib/msql uses 13Gb. and total of 18.6 Gb is used by filesystem.

To Fix this i have 3 Methods.

Manually delete Log files.
Using MySQL (Only works if mysql is starts)
Set Persist binlog settings(this will automatically delete logs after number of days you set)

Ok Lets get started.

Method #1 Manually Delete Log files.

you need to change directory to /var/lib/mysql, if you type type "du-bsh *" you can find your logs some thing like this, for tutorial i have only listed binlog files you can see the file name binlog.000141 to binlog.000148 these are the files which consumes most of you filesystem.


root@coversunkochi:/var/lib/mysql# du -bsh *
48M     /var/lib/mysql/binlog.000141
102M    /var/lib/mysql/binlog.000142
67M     /var/lib/mysql/binlog.000143
104M    /var/lib/mysql/binlog.000144
102M    /var/lib/mysql/binlog.000145
101M    /var/lib/mysql/binlog.000146
103M    /var/lib/mysql/binlog.000147
44M     /var/lib/mysql/binlog.000148

you can also find bindlog.index file this contains log files name, you be careful to do some thing stupid, you need take a backup first, then edit this file and remove indexing "remove names of logs" then save this.
after that you can delete files which is not in the index
now you can restart msyql it will start.

Method #2 Using MySQL

If you MySQL is still working you need to access MySQL then type following command, login to MySQL.


mysql> SHOW BINARY LOGS;
+---------------+-----------+-----------+
| Log_name      | File_size | Encrypted |
+---------------+-----------+-----------+
| binlog.000141 |  50260145 | No        |
| binlog.000142 | 106706425 | No        |
| binlog.000143 |  69240464 | No        |
| binlog.000144 | 108516594 | No        |
| binlog.000145 | 106324989 | No        |
| binlog.000146 | 105725450 | No        |
| binlog.000147 | 107466759 | No        |
| binlog.000148 |  98082094 | No        |
+---------------+-----------+-----------+

this will list your binary logs index, to delete logs to a certain number, i am going to delete binlog.000141 so i need to type command like this, the number mentioned below is the number of log which should apper in index file after removing, so in our case 141 will be deteted or all logs from 1 to 141 and rest of the logs will remain.


mysql> PURGE BINARY LOGS TO 'binlog.000142';

I have put MySQL logs for comparison before and after doing the purge.


mysql> SHOW BINARY LOGS;
+---------------+-----------+-----------+
| Log_name      | File_size | Encrypted |
+---------------+-----------+-----------+
| binlog.000141 |  50260145 | No        |
| binlog.000142 | 106706425 | No        |
| binlog.000143 |  69240464 | No        |
| binlog.000144 | 108516594 | No        |
| binlog.000145 | 106324989 | No        |
| binlog.000146 | 105725450 | No        |
| binlog.000147 | 107466759 | No        |
| binlog.000148 |  98082094 | No        |
+---------------+-----------+-----------+
8 rows in set (0.01 sec)

mysql> PURGE BINARY LOGS TO 'binlog.000142';
Query OK, 0 rows affected (0.01 sec)

mysql> SHOW BINARY LOGS;
+---------------+-----------+-----------+
| Log_name      | File_size | Encrypted |
+---------------+-----------+-----------+
| binlog.000142 | 106706425 | No        |
| binlog.000143 |  69240464 | No        |
| binlog.000144 | 108516594 | No        |
| binlog.000145 | 106324989 | No        |
| binlog.000146 | 105725450 | No        |
| binlog.000147 | 107466759 | No        |
| binlog.000148 |  98195420 | No        |
+---------------+-----------+-----------+
7 rows in set (0.00 sec)

Method #3 Set Persist binlog settings.

Now we can set automatically delete old log files!

In MySQL 8.0, use binlog_expire_logs_seconds instead, where the default value is 2592000 seconds (30 days). In this example, we reduce it to only 3 days (60 seconds x 60 minutes x 24 hours x 3 days):


mysql> SET GLOBAL binlog_expire_logs_seconds = (60*60*24*3);
Query OK, 0 rows affected (0.00 sec)

mysql> SET PERSIST binlog_expire_logs_seconds = (60*60*24*3);
Query OK, 0 rows affected (0.01 sec)

Enjoy.

SET PERSIST will make sure the configuration is loaded in the next restart. Configuration set by this command is stored inside /var/lib/mysql/mysqld-auto.cnf.

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